Develop Reference

Having trouble with the math for a loan calculator program

This is a loan calculator program. I'm having trouble with the math. Everything else seems to be correct except for the value of the beginning balance after 2 months. Notice that the beginning balance of the 3rd month is different from the ending balance of the 2nd month. Same thing for the succeeding months. I've been trying to fix it but everything didn't work out. I need them to be the same so the ending balance of the last month will be 0.
This is a sample output of the program:
Personal Loan Payment Calculator
Enter a loan amount: 1000
Enter the loan term (months): 6
Enter the interest rate (% per year): 9
Loan Payment and Amortization Table
Months Beginning Monthly Principal Interest Ending
Balance Payment Paid Paid Balance
1 1000.00 171.07 163.57 7.50 836.43
2 836.43 171.07 164.80 6.27 671.64
3 670.41 171.07 166.04 5.03 504.37
4 501.88 171.07 167.30 3.76 334.57
5 330.78 171.07 168.59 2.48 162.19
6 157.06 171.07 169.89 1.18 -12.83
Summary:
========
Loan Amount: $1,000.00
Monthly Payment: $171.07
Number of Payments: 6
Total Interest Paid: $24.00
Annual Interest Rate: 9.00%
This is the program:
public class LoanCalculator {
public static void main(String[] args) {
System.out.println("Personal Loan Payment Calculator"); // print the name of the program
System.out.println("================================");
Scanner keyboard = new Scanner (System.in); // define a Scanner object attached to a keyboard
String badInput; // assign non-integer or non-double inputs to badInput
System.out.print("Enter a loan amount: "); // prompt the user to enter loan amount
while ( ! keyboard.hasNextDouble()) // is the first input value a double?
{
badInput = keyboard.next();
System.out.println("Error: expected a Double, encountered: " + badInput);
System.out.println("Please enter a loan amount in Double: ");
}
double loanAmount = keyboard.nextDouble(); // assign the first input to loanAmount
System.out.print("Enter the loan term (months): "); // prompt the user to enter number of months
while ( ! keyboard.hasNextInt()) // is the second input value an int?
{
badInput = keyboard.next();
System.out.println("Error: expected an Integer, encountered: " + badInput);
System.out.println("Please enter a loan term in Integer: ");
}
int loanTerm = keyboard.nextInt(); // assign the second input to loanTerm
System.out.print("Enter the interest rate (% per year): "); // prompt the user to enter the interest rate
while ( ! keyboard.hasNextDouble()) // is the first input value a double?
{
badInput = keyboard.next();
System.out.println("Error: expected an integer, encountered: " + badInput);
System.out.println("Please enter a loan amount in Double: ");
}
double interestRate = keyboard.nextDouble(); // assign the third input to interestRate
System.out.println(); // skip a line
System.out.println(" Loan Payment and Amortization Table");
System.out.printf("%s", "=============================================================");
System.out.println();
System.out.printf("%5s %10s %10s %10s %10s %10s", "Months" ,"Beginning", "Monhtly", "Principal", "Interest", "Ending");
System.out.println();
System.out.printf(" %5s %10s %10s %10s %10s %10s", "#","Balance", "Payment", "Paid", "Paid", "Balance");
System.out.println();
System.out.printf("%s ", "=============================================================");
System.out.println();
double monthlyRate = (interestRate / 100.0) / 12.0;
double monthlyPayment = (monthlyRate * loanAmount) / ( 1 - (Math.pow( 1 + monthlyRate, - loanTerm)));
double beginningBalance = loanAmount;
double interestPaid = beginningBalance * monthlyRate;
double principalPaid = monthlyPayment - interestPaid;
int total_interest_paid = 0;
for (int monthCount = 0 ; monthCount < loanTerm ; ++monthCount)
{
int months = 1 + monthCount;
beginningBalance = loanAmount - principalPaid * monthCount;
interestPaid = beginningBalance * monthlyRate;
principalPaid = monthlyPayment - interestPaid;
double endingBalance = beginningBalance - principalPaid;
System.out.printf(" %5d %10.2f %10.2f %10.2f %10.2f %10.2f\n", months, beginningBalance, monthlyPayment, principalPaid, interestPaid, endingBalance);
total_interest_paid += interestPaid;
}
System.out.printf("%s ", "=============================================================");
System.out.println();
NumberFormat currency = NumberFormat.getCurrencyInstance();
DecimalFormat percentFormat = new DecimalFormat ("0.00");
System.out.println("\nSummary:");
System.out.println("========");
System.out.println("Loan Amount: " + currency.format(loanAmount));
System.out.println("Monthly Payment: " + currency.format(monthlyPayment));
System.out.println("Number of Payments: " + loanTerm);
System.out.println("Total Interest Paid: " + currency.format(total_interest_paid));
System.out.println("Annual Interest Rate: " + percentFormat.format(interestRate) + "%");
}
}

The error is very simple:
beginningBalance = loanAmount - principalPaid * monthCount;
Remember that "principalPaid" increases every month. The total principal paid is not the last principalPaid * mouthCount but the sum of the principal paid in all months.
You could create a running total for principalPaid like you did for interest paid.
But it would be much easier to do beginningBalance = previous month endingBalance.

Money format - how do I use it?

I'm a junior in high school. Having a tough time figuring out how to use money format. I'm doing an exercise in A Guide to Programming in Java (Second Edition) where I have to prompt the employees for the number of burgers, fries, and sodas.
Fries are $1.09, burgers are $1.69, and sodas are $0.99.
Here is my code:
import java.util.Scanner;
/**
* Order pg. 101
*
* Garret Mantz
* 2/10/2016
*/
public class Order {
public static void main(String[]args) {
final double pburgers=1.69;
final double pfries=1.09;
final double psodas=0.99;
final double ptax=0.065;
double burgers;
double fries;
double sodas;
double totaltax;
double total;
double tax;
double tendered;
double change;
Scanner input = new Scanner(System.in);
System.out.print("Enter the amount of burgers: ");
burgers = input.nextDouble();
System.out.print("Enter the amount of fries: ");
fries = input.nextDouble();
System.out.print("Enter the amount of sodas: ");
sodas = input.nextDouble();
System.out.print("Enter the amount tendered: ");
tendered = input.nextDouble();
totaltax = (burgers*pburgers)+(fries*pfries)+(sodas*psodas);
tax = totaltax*ptax;
total = totaltax + tax;
change = tendered - total;
System.out.println("Your total before tax is: \n" + totaltax);
System.out.println("Tax: \n" + tax);
System.out.println("Your final total is: \n" + total);
System.out.println("Your change is: \n" + change);
}
}
I just want to use the money format, but I'm not sure how. I'm sure it's a dumb question, but thank you for helping out!

Change your println to these, and see if that helps:
System.out.format("Your total before tax is: $%-5.2f\n", totaltax);
System.out.format("Tax: $%-5.2f\n", tax);
System.out.format("Your final total is: $%-5.2f\n", total);
System.out.format("Your change is: $%-5.2f\n", change);
There is also this:
NumberFormat formatter = NumberFormat.getCurrencyInstance();
String totalTaxString = formatter.format(totaltax);
String taxString = formatter.format(tax);
String totalString = formatter.format(total);
String changeString = formatter.format(change);
System.out.format("Your total before tax is: %s\n", totalTaxString);
System.out.format("Tax: %s\n", taxString);
System.out.format("Your final total is: %s\n", totalString);
System.out.format("Your change is: %s\n", changeString);
Output:
Your total before tax is: $8.53
Tax: $0.55
Your final total is: $9.08
Your change is: $10.92

ParadiseInfo2 variable error code

import java.util.Scanner;
public class ParadiseInfo2
{
public static void main(String[] args)
{
double price;
double discount;
double savings;
Scanner keyboard = new Scanner(System.in);
System.out.print("Enter cutoff price for discount >>");
price = keyboard.nextDouble();
System.out.print("Enter discount rates as a whole number >> ");
discount = keyboard.nextDouble();
System.out.println("Special this week on any service over " +
price);
System.out.println("Discount of " + discount + " percent");
System.out.println("That's a savings of at least $" + savings);
displayInfo();
savings = computeDiscountInfo(price, discount);
}
public static void displayInfo()
{
System.out.println("Paradise Day Spa wants to pamper you.");
System.out.println("we will make you look good.");
}
public static double computeDiscountInfo(double pr, double dscnt)
{
double savings;
savings = pr * dscnt / 100;
return savings;
}
}
I keep getting the following error on the above code. I can't figure out how to fix it. Thanks for all of your help!
ParadiseInfo2.java:18: error: variable savings might not have been
initialized
System.out.println("That's a savings of at least $" + savings);

The last line of main sets savings but you use it before then to print it. Change it to something like
// System.out.println("That's a savings of at least $" + savings);
displayInfo();
savings = computeDiscountInfo(price, discount);
System.out.println("That's a savings of at least $" + savings);

Separate two loops in java

I should write a program that reads balance and interest rate, and displays the value of the account in ten years with anually, monthly and daily compounds.
I have written for yearly compounding and for monthly. In the second loop for monthly rate, program reads value of "balance" after compounding yearly, while I need it read primary value. How is it possible to separate two loops, so they do not influence each other? Here is my code:
import java.util.Scanner;
public class BankInterest {
public static void main(String []args) {
System.out.println("Please enter your balance: ");
Scanner keyboard = new Scanner(System.in);
double balance = keyboard.nextDouble();
int years = 0;
int months = 0;
int days = 0;
System.out.println("Please enter the ann1ual interest rate in decimal form: ");
double interestRate = keyboard.nextDouble();
while (years<10) {
double interest = balance * interestRate;
balance = balance + interest;
years++;
}
System.out.println("Balance after 10 years with annual interest is " + balance);
while (months<120) {
double interest = balance * interestRate/12;
balance = balance + interest;
months++;
}
System.out.println("Balance after 10 years with monthly interest rate is " + balance);
}
}
When program is run and I input 100 for balance and 0.02 to interest rate, yearly compounding works well and displays:
Balance after 10 years with annual interest is 121.89944199947573
And second loop takes this value as balance and displays:
Balance after 10 years with monthly interest rate is 148.86352955791543
While, if my code was right it should display this number: 122.119943386

You can place both loops in different functions and pass both balance and interesRate as arguments, like below.
import java.util.Scanner;
public class BankInterest {
static public double annualInterest(double balance, double interestRate) {
int years = 0;
while (years < 10) {
double interest = balance * interestRate;
balance = balance + interest;
years++;
}
return balance;
}
static public double monthlyInterest(double balance, double interestRate) {
int months = 0;
while (months < 120) {
double interest = balance * interestRate/12;
balance = balance + interest;
months++;
}
return balance;
}
public static void main(String args[]) {
Scanner keyboard = new Scanner(System.in);
System.out.println("Please enter your balance: ");
double balance = keyboard.nextDouble();
System.out.println("Please enter the ann1ual interest rate in decimal form: ");
double interestRate = keyboard.nextDouble();
System.out.println("Balance after 10 years with annual interest is " +
annualInterest(balance, interestRate));
System.out.println("Balance after 10 years with monthly interest rate is " +
monthlyInterest(balance, interestRate));
}
}

You need to declare two different variables for initial balance and updated balance so that you can access the original balance in both loops. I have shown this below.
public static void main(String []args) {
System.out.println("Please enter your balance: ");
Scanner keyboard = new Scanner(System.in);
double startingBalance = keyboard.nextDouble();
double finalBalance=0;
int years = 0;
int months = 0;
int days = 0;
System.out.println("Please enter the ann1ual interest rate in decimal form: ");
double interestRateYearly = keyboard.nextDouble();
double interstRateMonthly = interestRateYearly;
double interstRateDayliy = interestRateYearly;
while (years<10) {
double interest = startingBalance * interestRateYearly ;
finalBalance = startingBalance + interest;
years++;
}
System.out.println("Balance after 10 years with annual interest is " + finalBalance);
while (months<120) {
double interest = startingBalance * interstRateMonthly /12;
finalBalance = startingBalance + interest;
months++;
}
System.out.println("Balance after 10 years with monthly interest rate is " + finalBalance);
}
}

payroll : adding multiple array values

The question is to create a program that asks the user to input how many employees. Then with each employee, a name, hour pay rate, hours worked is entered. the results of the employee pay, overtime pay and total pay is calculated.
My dilemma is how to find the total of all the pays. all employees pay, all employees overtime pay and all employees total pay
ex. user input: 2 employees (creates two arrays)
two inputs(name, rate, hours worked) will be entered
two results (pay, overtime pay, total pay) will be calculated
how do you add the pays, the overtime pays and total pays from both employees?
this is the code ive come up with, but it needs work
import java.util.Scanner;
public class paycheck {
public static void main(String[] args)
{
Scanner input= new Scanner(System.in);
System.out.print("Enter number of Employees: ");
int numberOfEmp= input.nextInt();
int[] arrayList= new int[numberOfEmp];
for (int i = 0; i < arrayList.length; i++){
System.out.print("Enter Employee Name: ");
String empName= input.next();
System.out.print("Enter hourly rate: ");
int rate= input.nextInt();
System.out.print("Enter hours worked: ");
int hours=input.nextInt();
if (hours >=40)
{
double regPay= hours * rate;
double otPay = (hours-40) *(rate*1.5);
double totalPay= regPay + otPay;
System.out.print("\nEmployee name: " + empName+"\n Regular pay: " + regPay +"\n Overtime pay: " + otPay+ "\n Total pay: " + totalPay+ "\n"+ "\n");
}
else
{
double regPay= hours * rate;
double otPay =0;
double totalPay= regPay + otPay;
System.out.print("\nEmployee name: " + empName+ "\n Regular pay: " + regPay +"\n Overtime pay: " + otPay+ "\n Total pay: " + totalPay+ "\n"+ "\n");
}
}
}
}

why dont you keep three different variables , say allsalary , allovertime , allpay and keep on adding whenever any new employee is entered .

Create an employee object that holds the values you want to track.
Create an ArrayList of employees.
Create a while loop that allows the user to input a employee's info, and then asks the user if they would like to continue or stop. If they want to stop exit the loop and print your data.
If you create an employee object, you might want to give it a few static variables to keep track of total_pay, total_ot_pay, and other "totals" you want to track.